Isomerizing hydrocarbons



Patented June25, 1946 UNITED srA'rE ISOMERIZING PATE NT orF- ca r'rrmtocmous Halsted a. War-rick, West Englewood, N. 1., as-

signor to The Texas Company, New York, N. Y., a corporation oi Delaware No Drawing Application March 1a, 1943, Serial No. 479.639

branched chain character of saturated feed hydrocarbons.

The invention contemplates eiiecting isomerization with a liquid isomerization catalyst comprising a metallic halide-hydrocarbon complex and restoring the activit of the complex at intervals by treatment with a hydrocarbon of relatively lower molecular weight than the feed hydrocarbon normally being charged to the process.

In accordance with the invention a feed hydrocarbon such as normal pentane or a mixture of hydrocarbons such as a pentane-hexane fraction of straight-run naphtha is subjected to contact with a metallic halide-hydrocarbon complex catalyst in the presence of hydrogen halide under conditions of temperature such that isomerization constitutes the principal reaction. The isomerization treatment is advantageously carried out in a continuous manner, the flow of feed hydrocarbons in contact with the complex catalyst being continued for a substantial period of time. Thereafter the catalyst is subjected to contact with a stream of lower molecular weight hydrocarbons such as normal butane, the catalyst being maintained at a temperature not greater than the reaction temperature prevailing during treatment of the higher molecular weight feed hydrocarbons, and preferably at a somewhat lower temperature so as to avoid side reactions which would result in objectionable compiexiormation. The flow of lower molecular weight hydrocarbon through the reaction zone is continued in the presence of hydrogen halide for a period of time sufflcient to restore the activity of-the complex catalyst. Thereafter the normal operation is resumed.

More specifically it is contemplated continuing the flow of the higher molecular weight feed hydrocarbon through the complex catalyst mass for a period which may range from one to several days or until such time as the activity of the catalyst for lsomerizing the feed hydrocarbon has declined substantially. At this time the flow of feed hydrocarbon is temporarily discontinued or may be diverted from the reaction zone to an ad- Jacent reaction zone containing more active or recently activated catalyst. During the discontinuance of such flow normal butane is passed continuously through the ofistream reaction zone while maintained at a temperature of about 180 to 210 F. under which conditions isomerization of the normal butane also occurs. During continued flow of normal butane through the reaction zone v for a iew hours or more the activity of the complex catalyst is increased. The flow of normal butane may be continued for a period which may range from several hours to several days. ,Thereafter the flow of higher molecular weight feed hydrocarbon is resumed and continued until such time as the catalyst requires reactivation by further treatment with normal butane. lo

eiiecting isomerization of the hydrocarbons consists essentially of aluminumhalide-hydrocarbon complex and particularly a complex which is characterized by having a heat of hydrolysis in the range about 200 to 400 calories per gram of complex. Advantageously the complex is substantially free from undissolved solid aluminum halide. For example, the complex is free from solids that would be separated by centrifuging at about 3000 revolutions per minute for a period of 30 minutes in an A. P. I. centrifuge at about normal room temperature.

The complex may be prepared by reacting aluminum halide with a saturated aliphatic hydrogs carbon in the presence of hydrogen chloride at a temperature of about 200 -F. as will be described in more detail later.

At any rate it has been found that by emplo ing a liquid complex catalyst of the character in 30. question migration or aluminum halide from the reaction zone can apparently be completely.

avoided so that the'eifiuenthydrocarbon stream from the reaction zon will be free or at least substantially free from aluminum halide. This inllfivolvesan important advantage over the type of process which employs a solid catalyst, in which type of process a. large amount of aluminum halide is carried out of the reaction zone in the emuent hydrocarbon stream. to v It has been observed that a complex catalyst of this type when used for isomerizins Cs and higher molecular weisht hydrocarbons may lose its activity during continued use, loss of activity eins'reflected by a progressive decrease in the m degree 02 octane improvement in the converted hydrocarbons. During this continued use a decrease in the specific gravity of the complex, say from about 1.5 or 1.4 to 1.3 is observed, which indicates an increase in the hydrocarbon content oi the complex. It is preferred to maintain the gravity or the complex at least about 1.35 relative to water at 60 F.

Bestoration oi thecatalyst activity d the treatment with normal butane may involve else ylation reactions between a1 or iso butane It has been found that an efiective actalyst for and a portion of the hydrocarbon material which has become complexed with the aluminum halide during isomerization of the higher molecular temperature of about 180 to 210 F. The reaction is carried out in the presence of a small amount oi hydrogen chloride. During the first few hours I of the run the product is characterized by having a clear 0. F. R. M. octane number of about 79.6 as compared with a C. F. R. M. octane number of 60.8 for the feedfraction. Arter about 50 hours onstream the octane number of the product decreases to about 77.7. After about 80 hours onstream the octane number has decreased to about 69. o

Upon substituting normal butane for the pentane-hexane fraction and charging normal butane through the thus used complex catalyst while maintained at about 210 F. and in the presence of hydrogen chloride the yield of isobutane initially obtained would be about 27 mol per cent hi the normal butane charged. Upon continuing the flow of normal butane through the complex catalyst under these conditions the per cent conversion to isobutane is progressively increased so that after running for about 50 hours under thesewith normal butane as above described over a period ranging from about 1 to 2 days.

The reason for the unexpected increase in activity of the catalyst during the period that normal butane is being charged is not understood.

" It may be that a small portion of the normalbutane reacts with aluminum halide in the catalyst to form a new type of complex which activates the main catalyst body. n the other hand the increase in activity may be at least partly the result of a washing or scrubbing action by which certain heavier hydrocarbon constituents of the complex which form and accumulate during the treatment of the pentane-hexane fraction are selectively removed during the normal butane treatment.

Intermittent treatment or the catalyst with the normal butane under isomerizing conditions is preferred over continuous and simultaneous charging of normal butane and the higher molec..

ular weight teed hydrocarbon since the inter-' 7o ierenttemperature conditions is apparently more mittent type of operation carrledout under difeflective in activating the catalyst.

While mention has been made of isomerizing a I pentane-hexane'fraction of straight-run naphtha itis, or course, contemplated that the process'is from 1 to several days, following which the catalyst is again subjected to reactivating treatment applicable to the isomerization of any higher molecular weight saturated hydrocarbon having 5 to 7 or more carbon atoms per molecule at a temperature ranging from about 100 to 250 or 300 F.

However, it is of particular advantage in the isomerization of normal paraflins such as pentane and hexane.

The frequency of activation of the complex catalyst and also the length of the period of activation may be varied substantially from those indicated above. For example, the higher molecular weight feed hydrocarbon may be charged continuously for a period of less than 24 hours and then normal butane charged for a relatively short period of 1' or 2 hours.

As previously mentioned the complex may be formed by reacting a metallic halide such as aluminum chloride or aluminum bromide with a saturated hydrocarbon in the presence of hydrogen chloride. In starting up the operation it may be advantageous to employ a preformed complex obtained by reacting aluminum halide with a kerosene or kerosene fraction which is substantially free from olefin and aromatic hydrocarbons. The resulting complex is then charged to the reactor and a small amount of aluminum halide maybe added continuously or intermittently to the reaction zone throughout the period of operation, a small and corresponding amount of used complex being withdrawn ,from the reaction zone. In other words the addition of aluminum halide and the withdrawal of used complex is regulated so that the main body of liquid complex catalyst maintained within the reaction zone will be characterized by having a heat of hydrolysis not in excess of about 400 calories per gram of complex and preferably about 300 to 320. In preparing the preformed kerosene complex aluminum chloride and kerosene in proportion of aboutfil /4, pounds of aluminum chloride Per gallon of kerosene may be charged into a closed vessel. The temperature of the mixture is raised to about 200 F. and hydrogen chloride vapor-is injected until the pressure stabilizes at about 35 pounds per square inch gauge. The contents of the vessel are subjected to mixing and after several hours th pressure rises. Cracked gases are vented from the vessel until the pressure drops to about 25 pounds per square inch gauge and the vessel is again repressured to 35 pounds by the injection of hydrogen chloride. This venting and repressuring may be repeated 2 or 3 times during a period of 8 or 9 hours required for forming and stabilizing complex. The complex phase is separated from any hydrocarbon phase that may be resent prior to introduction to the reaction zone of the isomerization process.

In effecting the isomerization reaction the catalyst is promoted by the continual or intermittent addition of hydrogen chloride or other suitable hydrogen halide which may be injected in the,entering hydrocarbon stream or maybe separately injected to the reaction zone; The amount of hydrogen chloride so injected may amount to about 1 to 5% by weight of the feed I of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap- -pended claims.

1 claim: v l. A process of isomerizln'g' hydrocarbons by contact with a metallic halide-hydrocarbon complex isomerization catalyst which comprises passing a saturated higher molecular weight feed hydrocarbon containing at least 5 carbon atoms per molecule through a reaction zone containing said complex having essentially the isomerizlng action of aluminum chloride-hydrocarbon com- 1 plex with a heat of hydrolysis within the range 200-400 calories per gram of complex and maintained in the presence of hydrogen halide under conditions such that isomerization constitutes the principal reaction, continuing the flow of higher molecular weight feed hydrocarbon through the reaction zone until activity of the complex catalyst diminishes substantially, temporarily disconcomprises a hydrocarbon selected irom the group of hydrocarbons having from about 5 to 7 carbon atoms per molecule.

3. A process for isomerizing hydrocarbon by I contact with a metallic halide-hydrocarbon complex isomerization catalyst which comprises passing a saturated feed hydrocarbon of about 5 to 7 1 carbon atoms per molecule through a reaction zone containing a catalyst consisting essentially of aluminum halide-hydrocarbon complex maintained in the presence of hydrogen halide at a temperature in the range about 150 to 250 F.

'such that isomerization constitutes the principal reaction, continuing the flow of said feed hydrocarbon through the reaction zone until activity of 4. The process according to claim 3 in which.

the complex catalyst has a heat oihydrolysis in the range about 200 to 400 calories per gram of complex.

5. Theprocess according to claim 3 in which ing about 400 calories per gram of complex and is substantially free from undissolved solid aluminum halide.

6. A process for isomerizing hydrocarbons by contact with a metallic halide-hydrocarbon complex isomerization catalyst which comprises passing higher molecular weight reed hydrocarbons containing at least 5 carbon atoms per molecule through a reaction zone containing a, catalyst consisting essentially or aluminum halide-hydrm 1 carbon complex, said complex maintained in the presence or hydrogen halide under conditions such that isomerizationvconstitutes the principal reaction, continuing the flow of higher molecular weight feed hydrocarbon through the reaction zone until activity of the complex catalyst diminishes substantially. temporarily discontinuing passage of said'high molecular weight feed hydrocarbon through the complex catalyst, during said discontinuance passing a saturated C4 hydrocarbon through said reaction zone while maintained at substantially the reaction temperature efiective for isomerization of said C4 hydrocarbon, continuing the flow of said C4 hydrocarbon in the presence of hydrogen halide until activity of "the catalyst has increased substantially. and

thereafter resuming the flow of said higher molecular weight fe'ed hydrocarbon through the reaction zone. i I

7. The process method according to claim 6 in which the aluminum halide-hydrocarbon complex has a heat of hydrolysis in the range about 300-320 calories per gram'of complex,

'8. A process for isomerizing hydrocarbons by contact with a metallic halide-hydrocarbon com-- plex isomerization catalyst which comprises passing a saturated higher molecular weight Ieed hydrocarbon containing at least 5, carbon atoms per molecule through a reaction zone containing a catalyst consisting essentially of aluminum halide-hydrocarbon complex maintained in the presence of hydrogen halide at a temperature in the range about 150-250 F., such that isomerization constitutes theprincipal reaction, continuing the flow of said feed hydrocarbon through the reaction zone until activity of the catalyst diminishes substantially, temporarily discontinuing passage of said feed hydrocarbon through the reaction zone, during said discontinuance passing a paraflln of lower molecular weight than said feed hydrocarbon through said reaction zone cient to effect substantial isomerization or said while maintained atca temperature not greater than the aforesaid reaction temperature but sumlower molecular weight paraflin, continuing the flow of said lower molecular weight therethrough in the presence of hydrogen halide I until activity of the catalyst? has increased subthe complex has a heat-oi hydrolysi not exceed- 

